In the manufacture of certain machine components, or other objects, particularly parts which are injection molded of metal or of materials known as plastics, it is necessary to remove thin flange-like projections, or "flash", left along mold mating lines, and also to smooth the parts and round sharp corners to reduce the chance of later chipping. Such deflashing usually precedes other post mold finishing operations, such as stamping, painting, electrical-lead forming and the like. It has been done by hand, and by known techniques such as tumbling masses of parts in baskets or barrel-like devices, frequently while subjecting the parts to a blast of deburring, abrasive, impact media, for example bits of walnut shell, sand or very small beads.
The blast technique is, per se, very advantageous, and while the above-mentioned tumbling techniques have also proven very useful, they are subject to a number of limitations. Most existing methods and apparatus for tumbling parts to remove flash, and for exposing the surfaces and inner sections to impact cleaning with media, are limited to occasional loading and unloading of relatively large batches within a tumbling basket, or to utilization of a sloped rotating drum through which the parts progress while tumbling. Basket type batch systems present problems relating primarily to the need for laborious manual loading and unloading operations. In some cases, this has been done by manual tilting of the basket, or by removing it from its drive plate and turning it over to discharge the parts. Since both loading and unloading must be done through the same basket opening, it is obvious that a basket system is not well adapted to automated in-line operation. Further, it is difficult to position blast guns or impellor wheels so that they will discharge into the basket opening without interfering with loading and unloading.
While a sloped tumbling barrel permits loading of parts from one end and discharge from the other, such a barrel does not readily afford access to the parts for impact cleaning. In such a barrel the parts usually are allowed to "walk" down the incline of the barrel as they tumble, thus receiving a timed exposure to the tumbling action. However, the exposure of individual parts is not necessarily uniform, as some parts will tend to "run" through the barrel at much faster rates than others. Additionally, while the speed of rotation of the barrel can be changed, thus affording some control of tumbling characteristics, the mechanical configuration of the barrel cannot be changed conveniently to allow still greater control over the tumbling action of different types of parts. Additionally, small batches of parts will not receive the same exposure and tumbling action as large batches, without modification of the physical arrangement of the barrel.